Project 3: Factors Influencing Food Calcium Bioavailability Here we propose to build upon and extend a notably successful project begun under the earlier SCOR award. We propose to explore further questions concerning inhibitors/enhancers of calcium absorption. To do so, we will measure the effects of two fiber types (i.e., cellulose and psyllium), examine the influence of phytate-to-calcium molar ratio (i.e., monocalcium phytate and hexacalcium phytate), and assess the presence of inhibitors/enhancers of calcium absorption in bovine milk fractions. Our earlier study of oxalate effects will be extended by tests of common calcium-containing vegetables that differ in concentration of oxalate. We will also examine the bioavailability of calcium in several vegetables commonly consumed by some segments of the U.S. population and most residents of third world nations. We will measure the absorption of calcium from three types of cooked beans, examine the influence of pretreatment of beans with phytase, and compare calcium absorption from fermented and unfermented soybean preparations. We will also assess the bioavailability of calcium in the principal green vegetables consumed by the residents of Southeastern China. This project involves an ongoing collaboration with Purdue University food scientists, who will produce all the vegetables with intrinsic 45Ca labeling as well as carry out certain pilot testing with rats. The major components of the project will involve sets of three measurements of calcium absorption by a single-isotope method, carried out at four-week intervals in healthy premenopausal women. Our experience with the methodologic and procedural details is extensive.